38 driveshaft to pinion

[Scott H]

Taking the torque tube off the banjo I found a loose pin that went thru the driveshaft and into the splines on the pinion. This doesn't look right, as the pin looks sheared on one end and mushroomed on the other end.
Is this supposed to be a roll pin? If so, anybody know what size?
Thanking you all in advance..

P2280011 (640x480).jpg

P2280012 (640x480).jpg

[Scott H]

Okay, so I need a drive shaft lock pin for 10 spline rear, Mac's has them for $.95. Says I need two. Probably one at the front end that I haven't taken apart yet.

How are these installed or held in place?

[deuce lover]

Sent you a PM with instructions

[JM 35 Sedan]

If that pin sheared where is the other piece? You should check the condition of the splines on pinion and driveshaft for wear. Only one pin needed. Maybe MAC's just likes to sell extra parts . The pin gets peened or mushroomed at both end.

Correction: when I said only one pin I was thinking '35-'36 tubular driveshaft to pinion connection. '38 rear would most likely have a solid driveshaft connected to pinion with a splined coupling/sleeve that would have two pins. Sorry for the bad info.

[Scott H]

Deuce, got your PM and its exactly the info I needed, thank you.

John, the pinion splines look fine, just looks like the pin is plumb worn out.

[Pete]

Sponsored Links (Register now to hide all advertisements)

The only reason that pin breaks is the splines are worn.
A new pin will fail also..Reaming and fitting an oversize pin won't work either.
The only thing that will work is replacing the pinion and the coupling. Sometimes the driveshaft end is worn also.
The fix for any worn spline is replacment.

[Scott H]

Pete, sounds like you've got the voice of experience. Bummer for me, I didn't really want to get into taking out the pinion and having to reset the backlash.
The pinion splins really look okay, just look a bit polished is all. I wanted to take the end couling off the driveshaft for inspection and checking the backlash against the pinion splines. And it looks like the end of the driveshaft, the coupling, is welded to the driveshaft? It doesn't seem lik its a separate piece. I tried pulling the shaft out of the torque tube but its only coming out about 12 inches and then gets stuck. Rotating it doesn't seem like its bent.

[Lawson Cox]

Originally Posted by JM 35 Sedan

If that pin sheared where is the other piece? You should check the condition of the splines on pinion and driveshaft for wear. Only one pin needed. Maybe MAC's just likes to sell extra parts . The pin gets peened or mushroomed at both end.

If memory serves me correctly, there are two pins that go through the connecting sleeve, one for the pinion end and one for the drive shaft end. Correct?

[bobH]

On one of mine, I used a bolt & thin nut. I peened it so the nut can't come off. Forgot whether I used gr 5 or 8 ?? It's been that way for quite awhile. So far, so good. Maybe the experts here will say why I shouldn't have ?? Just a thought...

[Karl Wolf]

There used to be an aftermarket (my opinion) pin sold... This had a spring steel strap that went around the drive shaft- holes in the end for the pin to stick into... ( I have dissassembled a couple of rears that had these) The spring steel strap would hold the broken off ends of the pin so that they would not be left to roam, and maybe get into the pinion bearings- and destroy them... I would pick up a couple of those kits, If I could find them... Karl

[JM 35 Sedan]

Originally Posted by Lawson Cox

If memory serves me correctly, there are two pins that go through the connecting sleeve, one for the pinion end and one for the drive shaft end. Correct?

Yes Lawson, I was thinking '35-'36 based on Avatar picture. '38 rear would most likely have solid driveshaft connected to pinion with splined sleeve/coupling and two pins. My bad.

[deuce lover]

2 pins on the 6 spline sleeve.On the late 32-36 10 spline the sleeve or splined collar is welded on the driveshaft tube,so only 1 pin.I have heard of 10 spline pinions used up until 38 on commercial applications.

[Scott H]

A wealth of information! Thanks all. Will update after I mess with the driveshaft again, tomorrow after work sometime.

The chassis I'm working on is a '38 car frame and running gear, supposedly with about 40k miles on it.

The coupling sleeve is welded to the end of the driveshaft and has 1 hole all the way thru that corresponds to the hole in the pinion splined shaft.

[habbott]

The pin which holds the spline on the pinion what is the correct procedure to fit are these hammered cold or heated red then peen or should you make a peening tool to form the rivet head.

[Barry WNY]

The coupling is softer, pinion is hard. Before I yank it all apart I would see if it fits loose, if so spend the $20 or so on a new coupling and see how that fits. I tried a roll pin & it shattered, made a snug fit pin in the end.

[JWL]

If the pin is involved in recieving torque from the driveshaft, such as when the splines are worn, it will break. Period. The only way I have found to protect the pin is to machine the diameter, in the section which goes through the pinion shaft, to a slightly smaller diameter while leaving the areas which fit the coupler at full diameter. Saying that another way, the pin is necked down where it passes through the pinion shaft to prevent the back and forth bending cycles which happen as the car is driven in reverse and forward gears.

[DICK SPADARO]

Stop. If your drive shaft has a 6 spline coupler that is welded to the driveshaft you have an issue. The drive shaft should join the pinion with a coupler. This coupler is pinned to the drive shaft and then pinned to the pinion. The engine side actually floats in the u-joint. If you have a coupler pin that is broken or missing at the pinion connection you have an issue with the drive shaft or torque tube from a collision. There is only a rotational load on the drive shaft and this is locked to the pinion via the splines. The pin only positions the coupler. If the pin is sheared there is a chance that the drive shaft is bent or the torque tube is bent or the center support bearing is missing or non functional. A broken pin usually indicates your drive shaft is not running on true center, spinning it produces a slight jump rope effect on the shaft and the shaft shortens as it spins. The faster it spins the more shear load is placed upon the pin and after a period of time it finally fatigues and breaks. This does not have to be out of alignment very much and in not necessarily visible by just looking at it. You need to make sure that the center torque tube bearing is in good condition and then have the drive shaft checked for true at a drive shaft shop before you reassemble the unit.

[Scott H]

I got the driveshaft out of the torque tube, cleaned up and tested it on the pinion. It has just a tiny bit of backlash, so I'm going to try it with a new pin. I still plan to have the driveshaft checked for true and balance before I reinstall it.
I checked the bell gaskets with a mic and found them to be .007 on both sides, so I used those gaskets to reassemble.

The cleaned up rear axle assembly:
P3030011 (640x480).jpg

And some various attaching nuts:
P3030012 (640x480).jpg